To allow optimal use to be made of the options for an exhaust gas catalyst which converts the pollutants emitted from internal combustion engines, in particular hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), it is advantageous for the air/fuel ratio supplied to the internal combustion engine to be modified slightly about the lambda value 1.00. However, this requires that the control of the modulation actually specifies a correct average lambda value, or optionally, that a correction value is determined and the average lambda value used is correspondingly adapted.
A method is known from DE 102 20 336 A1 for operating an internal combustion engine equipped with a three-way catalyst, whereby in a forced excitation the lambda value of the air/fuel mixture is cyclically controlled to a rich and a lean setpoint value, and the rich phases and the lean phases are balanced with one another with regard to the quantity of oxygen stored in the catalyst or with regard to the air mass.
In light of the foregoing, the object of the present invention is to provide the simplest possible yet accurate method for determining a correction value for the lambda center position in the control of an internal combustion engine.